Term Index (I)

Astrophysics (Index)

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Term Index (I)

I:
- HI region (HI): cloud of neutral atomic hydrogen
- I band: photometric filter for near infrared light
- spectral line: dark or light line in a spectrum
- state of ionization: difference in an ion's electron count versus proton count
- Stokes parameters: means of describing a polarization state
I band: photometric filter for near infrared light
I Zw 18:
- I Zwicky 18 (I Zw 18,Zw I 18): blue compact galaxy with low metallicity
I Zw 36:
- Haro 29: a blue compact galaxy
I Zwicky 18 (I Zw 18,Zw I 18): blue compact galaxy with low metallicity
i-band:
- Hubble Ultra-Deep Field (HUDF): extremely detailed HST image of a small region of space
IAA:
- Academia Sinica Institute of Astronomy and Astrophysics (ASIAA,IAA): Taiwanese astrophysics research organization
IAC:
- Instituto de Astrofísica de Canarias (IAC): research institute on Canary Islands
IACT:
- Cherenkov detector: type of high energy photon or particle detector
Iapetus:
- moon: a planet's natural satellite, such as Earth's
- Saturn: second largest planet in the solar system
IAU:
- dwarf planet: round like a planet, only smaller
- FITS: IAU standard for data such as images
- galactic coordinate system (GCS): celestial coordinate system system based upon the galactic plane
- International Astronomical Union (IAU,UAI): association of professional astronomers
- Minor Planet Center (MPC): organization collecting and organizing minor planet data
IAU Circular:
- International Astronomical Union (IAU,UAI): association of professional astronomers
IAU galactic coordinate system:
- galactic coordinate system (GCS): celestial coordinate system system based upon the galactic plane
IAUC:
- International Astronomical Union (IAU,UAI): association of professional astronomers
IBAS:
- INTEGRAL: European gamma ray observatory-satellite
IBEX:
- Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
IBEX-Hi:
- Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
IBEX-Low:
- Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
IBIS:
- INTEGRAL: European gamma ray observatory-satellite
IC:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
IC 342: spiral galaxy in the Council of Giants
- Council of Giants: twelve large galaxies surrounding the Local Group
IC 342/Maffei Group:
- IC 342: spiral galaxy in the Council of Giants
ICAT:
- Canadian Institute for Theoretical Astrophysics (CITA,ICAT): national research organization at University of Toronto
ICE:
- ice: solid state of water
- ice giant: planet more massive than gas planets and less than rocky planets
- International Cometary Explorer (ICE): 1980s space mission flying by comets
- snow line: distance from protostar cool enough for water to condense
- superionic ice: odd state of water at high temperature and pressure
- water-ice planet: planet made entirely of water ice
ice dwarf:
- plutoid: Pluto-like dwarf planet
ice giant: planet more massive than gas planets and less than rocky planets
- giant planet: planet of more than 10 Earth masses
ice line:
- snow line: distance from protostar cool enough for water to condense
IceCube: neutrino detector at the South Pole
IceCube Neutrino Observatory:
- IceCube: neutrino detector at the South Pole
ICEMAG:
- Europa Clipper: planned Europa space probe
ICF:
- ionization correction factor (ICF): relations between ion abundances and element abundances
ICM:
- intracluster medium (ICM): hot plasma throughout a galaxy cluster
ICRF:
- International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
ICRF3:
- International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
ICRS:
- International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
idea gas law:
- Hayashi limit: limit on the temperature of a star dependent upon its mass and luminosity
ideal gas:
- ideal gas law: relates pressure, temperature, and volume
- Lane-Emden equation: form of equation of state for gas ball in hydrostatic equilibrium
ideal gas law: relates pressure, temperature, and volume
- electron degeneracy: electrons set free of atoms by the Pauli exclusion principle
- isothermal core: core region of a body of all the same temperature
- statistical mechanics: mechanical behavior based upon probability
IDFT:
- fast Fourier transform (FFT): efficient algorithm for calculating a discrete Fourier transform
IDL: interactive vector-oriented programming language
IDP:
- interplanetary medium (IPM): matter in the solar system around and between planets
IDS:
- Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
- Shane Telescope: 3.05 m reflector telescope at Lick Observatory
- Washington Double Star Catalog (WDS): modern database of double stars
IDV:
- variable star: star that varies in magnitude
IEO:
- near-Earth object (NEO): object orbiting the Sun that passes close to Earth
IFS:
- integral field spectrograph: spectrograph that captures images
IFTS:
- imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
IFU:
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
IFU Observation:
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- Sloan Digital Sky Survey (SDSS): imaging survey of 500,000,000 objects in 35% of sky
IGAS:
- Ulysses: space mission to observe the Sun from off the ecliptic
IGM:
- intergalactic medium (IGM): matter between galaxies
IGR:
- INTEGRAL: European gamma ray observatory-satellite
II:
- spectral line: dark or light line in a spectrum
- state of ionization: difference in an ion's electron count versus proton count
III:
- spectral line: dark or light line in a spectrum
- state of ionization: difference in an ion's electron count versus proton count
illumination: measure of light energy producing a telescope's image
Illustris Project: 2013-2015 series of cosmological simulations
IllustrisTNG Project:
- Illustris Project: 2013-2015 series of cosmological simulations
IMAGE: satellite mission to study magnetosphere
IMACS:
- Magellan Telescopes: pair of 6.5 m optical telescopes in Chile
- PRIMUS: spectrographic survey of galaxies out to redshift 1
image dissector:
- photomultiplier tube (PMT): electronic device to detect light
image dissector photomultiplier:
- photomultiplier tube (PMT): electronic device to detect light
image scale:
- plate scale: relation between angle and distance across an image
image slicer:
- integral field spectrograph: spectrograph that captures images
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
image stabilization: camera mechanism to compensate for movement
image stacking:
- stacking: combining images of the same object
Image-Dissector Scanner:
- Shane Telescope: 3.05 m reflector telescope at Lick Observatory
imager:
- eROSITA: Russian/German space X-ray telescope launched in 2019
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- Keck Planet Imager and Characterizer (KPIC): extreme AO upgrade under development for Keck
- SPHERE: VLT instrument for imaging exoplanets
Imager for Magnetopause-to-Aurora Global Exploration:
- IMAGE: satellite mission to study magnetosphere
imaging:
- Zeeman-Doppler imaging (ZDI): technique for imaging stellar magnetic fields
imaging atmospheric Cherenkov telescope:
- Cherenkov detector: type of high energy photon or particle detector
imaging Fourier transform spectrometer:
- imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
imaging spectrograph:
- imaging spectrometer: device to capture spectrum point-by-point of an image
imaging spectrometer: device to capture spectrum point-by-point of an image
- spectroscopy: measurement of light with various electromagnetic wavelengths
IMAPS:
- Interstellar Medium Absorption Profile Spectrograph (IMAPS): 1980s/1990s UV spectrometer
IMBH:
- black hole (BH): region of such high mass that light cannot escape
- ultraluminous X-ray source (ULX): X-ray source with luminosity between a star and an AGN
IMF:
- initial mass function (IMF): function describing initial mass of stars
IMPACT:
- impact: collision of one solid body with another
- STEREO: two-satellite system to observe the Sun
- Tillotson equation: equation of state for high speed impacts
impact erosion:
- impact: collision of one solid body with another
impact parameter:
- transiting planet: planet crossing between another body and the observer
IMPS:
- IRAS: 1983 satellite that surveyed the sky in infrared
IMRI:
- extreme mass ratio inspiral (EMRI): inspiraling pair of objects with mass ratio beyond 10,000
IMS:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
IMXB:
- binary star: system of two stars co-orbiting
in situ: on site
- cavity-enhanced absorption spectroscopy (CEAS): passing a beam through a gas multiple times to amplify absorption lines
in situ observation:
- in situ: on site
INAF:
- Astronet: European astronomy consortium
- Telescopio Nazionale Galileo (TNG): 3.58 m telescope in Canary Islands
incidence:
- Snell's law: optical principle of refraction
inclination:
- orbital element: parameters describing an orbit
- orbital inclination: angle between plane of an orbit and a reference plane
Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
Index Catalog of Visual Double Stars:
- Washington Double Star Catalog (WDS): modern database of double stars
Index Catalogue of Nebulae and Clusters of Stars:
- Index Catalog (IC): 1895 catalog of galaxies, star clusters, and other nebulae
index of refraction:
- twinkling: blinking, apparent movement and color changes of observed stars
India:
- Giant Metrewave Radio Telescope (GMRT): large radio interferometer in India
- LIGO-India: planned gravitational wave detector in India
- Ooty Radio Telescope (ORT): cylindrical radio telescope in India
- Vainu Bappu Observatory (VBO): observatory in southern India
Indian Initiative in Gravitational-wave Observations:
- LIGO-India: planned gravitational wave detector in India
INDIGO:
- LIGO-India: planned gravitational wave detector in India
inertial forces:
- Reynolds number (Re): measure reflecting a fluid system's propensity to turbulence
inertial frame of reference:
- inertial reference frame: frame of reference where no force means no acceleration
inertial mass:
- mass: object's quality that determines the effects of forces and gravity
inertial reference frame: frame of reference where no force means no acceleration
infall:
- dynamical friction: drag produced by gravitational interaction with surrounding objects
inferior planet:
- heliocentric system: model of the universe with the planets orbiting the Sun
infinitesimal transform:
- Lie transform: type of infinitesimal transform
infinitesimal transformation:
- Lie transform: type of infinitesimal transform
inflated gas giant:
- hot Jupiter (HJ): Jupiter-sized gas exoplanet orbiting very close to star
inflated radii: exceptionally large radii of some hot Jupiters
inflation: theorized rapid expansion of the very early universe
- cosmological simulation: simulation of the history of the universe
- initial fluctuations: early universe density variations leading to current universe
- primordial black hole: black holes forming at the most dense volumes when inflation ceased
inflation field:
- quantum fluctuations: short-lived particles popping up at random
inflation theory:
- inflation: theorized rapid expansion of the very early universe
inflationary theory:
- inflation: theorized rapid expansion of the very early universe
information:
- black-hole information paradox: a behavior of black holes that appears to contradict physics
infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- AFGL Four Color Infrared Sky Survey (AFGL): 1970s infrared survey
- AKARI: Japanese space infrared telescope
- ARIEL: planned space mission for exoplanet spectrography
- Atacama Submillimeter Telescope Experiment (ASTE): ten meter submillimeter telescope in Chile
- BOOMERanG: 1990s-2000s balloon-borne 1.3-meter millimeter telescope
- Canada-France-Hawaii Telescope (CFHT): 3.6 meter optical/infrared telescope in Hawaii
- Catalog of Infrared Observations (CIO): collection of infrared observation data from numerous sources
- CCAT: 25-meter submillimeter telescope plan for Chile
- CCAT-prime (CCAT-p): planned 6-meter submillimeter telescope in Chile
- Cerro Tololo Inter-American Observatory (CTIO): NOAO observatory in Chile with Blanco telescope
- Cosmic Background Explorer (COBE): 1989 satellite for observing the CMB
- cosmic infrared background (CIB,CIBR): widespread infrared radiation not associated with known sources
- CRIRES: high resolution IR echelle spectrometer
- Darwin: past plan for space telescopes acting as an interferometer
- electromagnetic spectrum: spectrum of EMR
- ESO 3.6m Telescope: reflector telescope at La Silla
- Euclid: planned observatory-satellite to measure dark energy
- European Southern Observatory Very Large Telescope (ESO VLT,VLT): four 8.2-meter optical telescopes in Chile that can act together
- far infrared (FIR,far-IR): infrared radiation with wavelengths in the 30-450 μm range
- FINESSE: planned space mission for exoplanet spectrography
- Fred Lawrence Whipple Observatory (FLWO): observatory near Amado, Arizona
- Gaia: 2010s astrometry survey satellite
- Galileo Observatory: infrared observatory-plane in the early 1970s
- Gemini Observatory: pair of telescopes in Hawaii and Chile
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- Gran Telescopio Canarias (GTC): 10.4 meter telescope in the Canary Islands
- Herschel Space Observatory: infrared observatory-satellite with 3.5 meter reflector
- High Definition Space Telescope (HDST): proposed 12 m space telescope
- Hubble Space Telescope (HST): observatory-satellite with 2.4 meter reflective telescope
- hyperluminous infrared galaxy (HLIRG, HyLIRG): a galaxy emitting a more far infrared than an ULIRG
- I band: photometric filter for near infrared light
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
- infrared dark cloud (IRDC): molecular cloud not emitting nor transmitting infrared
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
- Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
- IOTA: past optical interferometer in Arizona
- IPAC: Caltech group to collect and analyze infrared observations
- IRAS: 1983 satellite that surveyed the sky in infrared
- IRSA: archive center for infrared data from NASA missions
- IRTF: Mauna Kea 3-meter infrared telescope
- James Clerk Maxwell Telescope (JCMT): far-infrared telescope in Hawaii
- James Webb Space Telescope (JWST): future space-based 6.5 meter infrared telescope
- K band: atmospheric window centered around 2.2 microns, or 136 THz
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Kitt Peak National Observatory (KPNO): NRAO observatory in Arizona with Mayall telescope
- Kuiper Airborne Observatory (KAO): infrared observatory-plane in the 1980s
- Large Binocular Telescope (LBT): dual 8.4 meter telescope in Arizona
- Large Millimeter Telescope (LMT): large microwave telescope in Mexico
- LiteBIRD: planned spacecraft to map CMB polarization
- low-surface-brightness galaxy (LSB galaxy): galaxies less bright than those historically identified
- Lowell Discovery Telescope (LDT,DCT): 4.3 m telescope at Lowell Observatory, Arizona
- luminous infrared galaxy (LIRG): a galaxy emitting a lot of far-infrared light
- LUVOIR: plan for a space-based telescope
- Magellan Telescopes: pair of 6.5 m optical telescopes in Chile
- MAXIMA: 1998-1999 balloon-borne 1.3-meter millimeter telescope
- mid infrared (MIR,mid-IR): infrared radiation with wavelengths in the 7.5-25 μm range
- Midcourse Space Experiment (MSX): 1990s space telescope
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Munich Near-Infrared Cluster Survey (MUNICS): 1990s-2000s galaxy cluster survey
- near infrared (NIR,near-IR): electromagnetic radiation in the range of 800-2500 nm
- New Technology Telescope (NTT): 3.58-meter reflector telescope in Chile
- NIRPS: near-infrared extension to HARPS spectrograph
- obscured fraction-luminosity relation: relation between AGN luminosity and surrounding dust IR emission
- OH/IR source: AGB star with strong OH maser
- OIR: a spectral "band name" for both visible light and infrared
- Origins Space Telescope (OST): concept for future very large space IR telescope
- R band: band of visible light around 6500 angstroms
- Roman Space Telescope (RST,WFIRST): proposed near-infrared space observatory
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- SOFIA: aircraft-based infrared observatory
- SpeX: a medium-resolution infrared spectrograph
- SPICA: plan for a future space IR telescope
- SPIRou: CFHT spectropolarimeter for exoplanet research
- Spitzer Extragalactic Representative Volume Survey (SERVS): infrared survey of some well-studied fields
- Spitzer Space Telescope (SST): past a satellite with infrared telescope
- starburst galaxy: galaxy forming stars at a very high rate
- Subaru Telescope: 8.2 meter telescope in Hawaii
- submillimeter galaxy (SMG): galaxy that produces significant submillimeter radiation
- Submillimeter Telescope (SMT,HHSMT): 10 meter far-infrared telescope
- Telescopio Nazionale Galileo (TNG): 3.58 m telescope in Canary Islands
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- Two Micron All-sky Survey (2MASS): near-infrared survey of both hemispheres
- Two Micron Sky Survey (IRC,TMSS): 1969 infrared catalog produced by Caltech
- UKIDSS: five-part infrared survey using UKIRT
- ultraluminous infrared galaxy (ULIRG,ELF): a galaxy emitting a more far infrared than an LIRG
- United Kingdom Infrared Telescope (UKIRT): Mauna Kea 3.8 meter infrared telescope
- University of Tokyo Atacama Observatory (TAO): observatory for a 6.5 m infrared telescope under construction
- UVOIR: a spectral "band name" covering UV, visible light, and IR
- VISTA: 4.1 meter telescope in Paranal Observatory in Chile
- Wide Field Infrared Explorer (WIRE): partly-failed 1999 infrared satellite
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
Infrared Astronomical Satellite:
- IRAS: 1983 satellite that surveyed the sky in infrared
infrared astronomy:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
Infrared Catalog:
- Two Micron Sky Survey (IRC,TMSS): 1969 infrared catalog produced by Caltech
infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
infrared dark cloud (IRDC): molecular cloud not emitting nor transmitting infrared
infrared excess (IRX): more infrared than that of a star's typical spectrum
Infrared Imaging Surveyor:
- AKARI: Japanese space infrared telescope
infrared light:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
infrared luminosity:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
Infrared Optical Telescope Array:
- IOTA: past optical interferometer in Arizona
Infrared Processing and Analysis Center:
- IPAC: Caltech group to collect and analyze infrared observations
Infrared Science Archive:
- IRSA: archive center for infrared data from NASA missions
Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
Infrared Telescope Facility:
- IRTF: Mauna Kea 3-meter infrared telescope
Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
infrared window:
- atmospheric window: frequency bands within which the atmosphere passes EMR
ING:
- Isaac Newton Group of Telescopes (ING): three telescopes in Canary Islands
- Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
ingress duration:
- transiting planet: planet crossing between another body and the observer
INGRID:
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
initial fluctuation spectrum: the power spectral density of the early universe
initial fluctuations: early universe density variations leading to current universe
initial mass function (IMF): function describing initial mass of stars
INMS:
- Cassini: explorer spacecraft sent to Saturn
inner cloud:
- Hills cloud: cloud of comets and minor planets around the solar system
inner Lindblad resonance:
- Lindblad torque: torque due to Lindblad resonances
inner moon:
- Enceladus: Saturn moon considered possible carrier of life
inner Oort cloud:
- Hills cloud: cloud of comets and minor planets around the solar system
inner working angle:
- coronagraph: telescope feature to block light from a specific body
inner-Earth object:
- near-Earth object (NEO): object orbiting the Sun that passes close to Earth
innermost stable circular orbit (ISCO): border of region surrounding a BH in which orbits are unstable
INS:
- neutron star (NS): stellar remnant consisting entirely of solar masses of neutrons
insolation: solar energy received per unit area in given time
instability region: region around an object where orbits cannot persist
instability strip: region of H-R diagram where stars are unstable
Institut de radioastronomie millimétrique (IRAM): organized radio astronomy collaboration between France, Germany, and Spain
Institut für Theoretische Astrophysik:
- Institute of Theoretical Astrophysics (ITA): Heidelberg research institute
Institute for Pale Blue Dots:
- Carl Sagan Institute (CSI): group researching finding life on other planets and moons
Institute for Theoretical and Experimental Physics:
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
Institute of Theoretical Astrophysics (ITA): Heidelberg research institute
Instituto de Astrofísica de Canarias (IAC): research institute on Canary Islands
instrument:
- 4MOST: spectrograph in development for VISTA telescope
- ACBAR: instrument used in CMB search
- ACIS: imaging spectrometer on Chandra X-ray telescope
- CONCERTO: spectrometer aimed at mapping the [CII] line
- CorMASS: near-infrared spectrograph
- CRIRES: high resolution IR echelle spectrometer
- Dark Energy Spectroscopic Instrument (DESI): new instrument for measuring red-shift of distant objects
- G-CLEF: spectrograph on the GMT
- Gemini Planet Imager (GPI): infrared instrument to overcome signal noise imaging exoplanets
- GISMO: 2 mm bolometer camera on IRAM 30 m telescope
- GUPPI: radio-telescope back-end aimed at processing pulsar data
- HARPS: high-precision spectrograph for exoplanet searches
- HARPS-N: high-precision spectrograph for exoplanet searches in Canary Islands
- HERMES: four-channel spectrograph on the Anglo-Australian Telescope
- Keck Planet Finder (KPF): spectrograph in development for Keck
- Keck Planet Imager and Characterizer (KPIC): extreme AO upgrade under development for Keck
- KMOS: 2-micron spectrograph on ESO VLT
- linearly variable filter (LVF): filter whose passband varies over one spatial dimension
- Mimir: multi-function near-infrared instrument on Perkins Telescope
- Multi-object Optical and Near-IR Spectrograph (MOONS): advanced spectrograph under development for VLT
- MUSTANG: bolometer array on the Green Bank Telescope
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- NIRPS: near-infrared extension to HARPS spectrograph
- PAMELA: cosmic ray detector attached to satellite
- plate measuring machine (APM): machine to measure position of images on photographic plates
- POLARBEAR: instrument to map CMB polarization
- PUPPI: Arecibo radio-telescope instrument aimed at observing pulsars
- QUEST: sixteen square-degree survey camera
- SCUBA: submillimeter instrument on James Clark Maxwell Telescope
- SpeX: a medium-resolution infrared spectrograph
- SPHERE: VLT instrument for imaging exoplanets
- SPIRou: CFHT spectropolarimeter for exoplanet research
- TAIPAN: multi-object spectrograph with robot fiber-positioner
- TolTEC: sensitive infrared camera under construction for the LMT
- Tomographic Ionized-carbon Mapping Experiment (TIME): proposed instrument to map the [CII] line
- TripleSpec (TSpec): near-infrared spectrograph on the Hale Telescope
- WEAVE: spectrograph under construction for the William Herschel Telescope
- Wide-field Multi-object Spectrograph (WFMOS): proposed instrument to detect baryon acoustic oscillations
instrument type:
- bolometer: instrument measuring heat produced by radiation
- CCD: electronic device to detect light
- Cherenkov detector: type of high energy photon or particle detector
- collimator: device to align beams of light
- downconverter: device that reduces the frequency of a signal
- Fabry-Pérot interferometer (FPI): type of chromatic-dispersing interferometer
- fiber positioner: machine to set up fibers in multi-object spectrograph
- Geiger-avalanche photodiode (G-APD,SPAD): type of solid state photon sensor
- gravitational-wave detector: device to detect gravitational waves
- imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- KID: type of sensitive electronic device to detect light
- Langmuir probe (LP): plasma sensor
- magnetometer: instrument to measure the strength of a magnetic field
- mass spectrometer: device to determine the mass of molecules in a mixture
- meridian circle: instrument for timing the passage of stars over a meridian
- multi-object spectrograph: device to record the spectrum of multiple targets simultaneously
- multichroic feedhorn array: radio array with sensors for two or more bands
- neutron spectrometer: device determining the energy of received free neutrons
- particle spectrometer: device to determine the characteristics of incoming particles
- photodiode: class of solid state device to detect EMR
- photometer: instrument measuring brightness
- photomultiplier tube (PMT): electronic device to detect light
- radar: probe based on reflecting radio waves
- radiometer: device for measuring radiant flux
- scintillator: instrument part designed to respond to high-energy photons
- sounder: device to measure something at another depth
- spark chamber: type of ion detector
- spectrograph: device to record the spectrum of incoming light
- spectrometer: device to measure light by wavelength across its spectrum
- spectroscope: device to study the spectrum of incoming light
- superconducting tunnel junction (STJ): type of Josephson junction usable in EMR sensors
- telescope: instrument to observe at a distance
- transition edge sensor (TES): sensor using superconduction's strong temperature sensitivity
- wavefront sensor: instrument for determining a wave's deformation
instruments:
- adaptive optics (AO): optical instruments that dynamically adapt to atmospheric distortion
- back end instrument: instruments of a telescope that process or combine signals
- collecting area: cross-sectional area over which a telescope receives EMR
- emissivity: measure of a material's efficiency at radiating thermal radiation
- etalon: two parallel reflective surfaces separating light according to wavelength
- extreme adaptive optics (ExAO): high-performance version of AO system
- focal plane array (FPA): array of receivers at the focus of a radio telescope
- frequency modulation (FM): changing the frequency of a signal's carrier
- front end instrument: instruments of a telescope that detect and encode the signal
- grism: combination of a grating and a prism
- hot pixel: CCD pixel that shows more brightness than it should
- integration time: time required to acquire signal
- Lyot stop: optical element to block unwanted light within instruments
- optical axis: center line through an optical instrument
- optics: science and technology regarding visible light
- photon counting: sensing EMR down to the photon level
- photon noise: variation in light measurement due to its quantum nature
- quantum efficiency (QE): measure of instrument's ability to sense EMR
- speckle suppression: methods of reducing noise in telescope observations
- spectral resolution: measure of a spectrograph's ability to resolve features of the spectrum
- systematic error: errors with non-random characteristics
- thermal noise: noise inherent in electronic component warmer than absolute zero
- wavefront error (WFE): measure of a telescope's distortion of incoming waves
INT:
- IPHAS: H-alpha survey
- Isaac Newton Group of Telescopes (ING): three telescopes in Canary Islands
- Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
- Millennium Galaxy Catalogue (MGC): 2000s catalog of 10,000 galaxies
- POINT-AGAPE: survey of M31 for microlensing
- Roque de los Muchachos Observatory (ORM,LPO,NHO): observatory at La Palma in the Canary Islands
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
INT Photometric H-alpha Survey of the Northern Galactic Plane:
- IPHAS: H-alpha survey
INT Photometric Halpha Survey:
- IPHAS: H-alpha survey
INTEGRAL: European gamma ray observatory-satellite
- integral field spectrograph: spectrograph that captures images
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
INTEGRAL Burst Alert System:
- INTEGRAL: European gamma ray observatory-satellite
integral field spectrograph: spectrograph that captures images
integral field spectrometer:
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
integral field spectroscopy:
- integral field spectrograph: spectrograph that captures images
integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- imaging spectrometer: device to capture spectrum point-by-point of an image
- integral field spectrograph: spectrograph that captures images
integrated Sachs-Wolfe effect:
- Sachs-Wolfe effect (SWE,SWeffect): gravitational redshift of the CMB
integration time: time required to acquire signal
intensity: power reaching a surface from a specific source
intensity map:
- intensity mapping: measure of cosmic matter density
intensity mapping: measure of cosmic matter density
- foreground subtraction: removing unwanted sources of EMR in intensity mapping
Interactive Data Language:
- IDL: interactive vector-oriented programming language
interference: result of interaction of waves
- radio frequency interference (RFI): transmissions in a frequency band under observation
interference pattern:
- interference: result of interaction of waves
interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- Allen Telescope Array (ATA): array of radio telescopes in northern California for SETI
- Atacama Large Millimeter Array (ALMA): large radio telescope array in Chile
- Australia Telescope Compact Array (ATCA): radio telescope in eastern Australia
- Australian Square Kilometre Array Pathfinder (ASKAP): radio telescope array of 36 12-meter dishes
- Canada-France-Hawaii Telescope (CFHT): 3.6 meter optical/infrared telescope in Hawaii
- CHARA: optical interferometer
- COAST: optical interferometer in England
- Combined Array for Research in Millimeter-wave Astronomy (CARMA): array of radio telescopes in eastern California
- Cosmic Anisotropy Telescope (CAT): 1990s interferometer to measure CMB variations
- Cosmic Explorer: concept for a very large LIGO-like GW detector
- Darwin: past plan for space telescopes acting as an interferometer
- DASI: 2000-2003 South Pole CMB telescope
- Einstein Telescope: concept for a larger LIGO-like GW detector
- GEO600: ground-based gravitational-wave detector in Germany
- GI2T: optical interferometer in France
- Giant Metrewave Radio Telescope (GMRT): large radio interferometer in India
- IOTA: past optical interferometer in Arizona
- KAGRA: gravitational wave detector in Japan preparing for operation
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- LIGO: pair of observatories to detect gravitational waves
- LIGO-India: planned gravitational wave detector in India
- LISA: proposed space mission to detect gravitational waves
- Navy Precision Optical Interferometer (NPOI): optical interferometer in Arizona
- New Gravitational Wave Observatory (NGO): past proposal for space mission to detect gravitational waves
- Next Generation Very Large Array (ngVLA): planned radio telescope array as a follow-on to ALMA and the Jansky VLA
- Palomar Testbed Interferometer (PTI): near-infrared interferometer experiment
- PAPER: radio interferometer for 21-cm measurement
- Plateau de Bure Interferometer (PdBI): 6-dish interferometer in French Alps
- Square Kilometre Array (SKA): radio telescope collecting a square kilometer
- Submillimeter Array (SMA): radio interferometer in Hawaii
- TAMA 300: small prototype gravitational wave detector in Japan
- Very Large Array (VLA): radio telescope in New Mexico
- Very Long Baseline Array (VLBA): radio interferometer stretching 8000 km
- Very Small Array (VSA): radio interferometer in Canary Islands
- Virgo: ground-based gravitational-wave detector in Italy
- Yuan-Tseh Lee Array (YTLA,AMiBA): microwave interferometer in Canary Islands
interferometry: analysis of superimposed EMR waves
- aperture synthesis: interferometry to simulate a larger aperture telescope
- Astronomical Image Processing System (AIPS): software for processing radio astronomy data
- baseline: distance between dishes of an interferometer
- correlator: unit that interferes wave signals for interferometry
- Earth-sized VLBI: ground-based VLBI with near-maximal baseline
- electronic very-long-baseline interferometry (e-VLBI): real-time VLBI using electronic links
- Fabry-Pérot interferometer (FPI): type of chromatic-dispersing interferometer
- interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- optical interferometer: interferometer of visible light
- spectral correlator: correlator that also functions as a spectrograph
- very-long-baseline interferometry (VLBI): interferometry based upon storing timing data at each telescope
intergalactic clouds:
- Lyman-alpha forest: overlaid redshifted Lyman-alpha absorption lines on light from distant objects
intergalactic medium (IGM): matter between galaxies
interloper:
- intensity mapping: measure of cosmic matter density
intermediate band photometry:
- photometry: studying starlight through bandpass filters
intermediate mass ratio inspiral:
- extreme mass ratio inspiral (EMRI): inspiraling pair of objects with mass ratio beyond 10,000
intermediate polar:
- variable star: star that varies in magnitude
intermediate spiral galaxy:
- NGC 6946: face-on spiral galaxy
intermediate-mass black hole:
- black hole (BH): region of such high mass that light cannot escape
- extreme mass ratio inspiral (EMRI): inspiraling pair of objects with mass ratio beyond 10,000
- ultraluminous X-ray source (ULX): X-ray source with luminosity between a star and an AGN
intermediate-mass X-ray binary:
- binary star: system of two stars co-orbiting
intermediate-velocity cloud:
- high-velocity cloud (HVC): fast-moving clouds in galactic halos
internal gravity wave: ripples in a change in density in a fluid
internal wave:
- internal gravity wave: ripples in a change in density in a fluid
International Astronomical Union (IAU,UAI): association of professional astronomers
- FITS: IAU standard for data such as images
- galactic coordinate system (GCS): celestial coordinate system system based upon the galactic plane
- Minor Planet Center (MPC): organization collecting and organizing minor planet data
International Atomic Time:
- terrestrial time (TT): current measure of time for astronomical observations on Earth
International Celestial Reference Frame:
- International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
International Celestial Reference System (ICRS): standardized variation of equatorial coordinate system
International Cometary Explorer (ICE): 1980s space mission flying by comets
International Gamma-ray Astrophysics Laboratory:
- INTEGRAL: European gamma ray observatory-satellite
International Pulsar Timing Array (IPTA): organization of pulsar timing arrays
International Robotic Antarctic Infrared Telescope:
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
International Solar Polar Mission:
- Ulysses: space mission to observe the Sun from off the ecliptic
International Space Station:
- MAXI: Japanese X-ray camera on the International Space Station
- NICER: space X-ray mission specifically to view neutron stars
International Sun-Earth Explorer:
- International Cometary Explorer (ICE): 1980s space mission flying by comets
International System of Units:
- SI: modern metric system
International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
International Virtual Observatory Alliance:
- virtual observatory (VO): online database of astronomical data
interplanetary dust particle:
- interplanetary medium (IPM): matter in the solar system around and between planets
interplanetary medium (IPM): matter in the solar system around and between planets
interpretation:
- CO to H₂ factor (Xco,X_CO): assumed ratio between observed CO emission lines and H₂ mass
interstellar astronomy:
- interstellar astrophysics: astronomy of the ISM including dust and clouds
interstellar astrophysics: astronomy of the ISM including dust and clouds
Interstellar Boundary Explorer (IBEX): satellite observing the ISM/heliosphere boundary
interstellar cloud:
- cloud: higher-density region of space
interstellar dust:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
interstellar extinction:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
interstellar magnetic field (ISMF): galactic magnetic field between that of stars
interstellar medium (ISM): matter within a galaxy between star systems
- shell: hollow shaped region of some kind of ISM
- supershell: very large ISM shell-shaped region
Interstellar Medium Absorption Profile Spectrograph (IMAPS): 1980s/1990s UV spectrometer
interstellar reddening:
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
interstellar scintillation:
- scintillometry: measuring of twinkling
intertropical convergence zone (ITCZ): circulation pattern near equator where north and south Hadley cells meet
intracluster gas:
- intracluster medium (ICM): hot plasma throughout a galaxy cluster
intracluster medium (ICM): hot plasma throughout a galaxy cluster
intraday variable:
- variable star: star that varies in magnitude
intrinsic color index:
- color index: a number that characterizes the color of an object
intrinsic S-star:
- S-type star (S): type of star with lines indicating zirconium
inverse beta decay:
- neutronization: an electron and proton combining to form a neutron
inverse bremsstrahlung:
- bremsstrahlung: photon emission when a charged particle is decelerated
inverse Compton:
- Compton scattering: photon collision with a charged particle that emits a different photon
inverse Compton scattering:
- Compton scattering: photon collision with a charged particle that emits a different photon
- Sunyaev-Zel'dovich effect (SZ effect,SZ,SZE): type of distortion of the CMB
- synchrotron self-Compton (SSC): charged particle cloud scattering its own synchrotron-produced photons
inverse discrete Fourier transform:
- fast Fourier transform (FFT): efficient algorithm for calculating a discrete Fourier transform
inverse Fourier transform:
- Fourier transform: systematic method of breaking down functions into periodic components
inverse model:
- forward model: model producing potential observable values from parameters
inverse Radon transform:
- tomography: observation of sections of a 3D object
inverse square law: a value's dependency upon reciprocal of the square of the distance from something
inverse volume weighting:
- volume weighting: method of accommodating the Malmquist bias
Io: well-known Jupiter moon
Io plasma torus:
- Io: well-known Jupiter moon
Io torus:
- Io: well-known Jupiter moon
ion: non-neutral atom or molecule, with missing or extra electrons
- C⁺: ionized carbon missing one electron
- solar energetic particle (SEP): high-energy particles from the Sun
- state of ionization: difference in an ion's electron count versus proton count
ion engine: type of electrical spacecraft engine
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
ion thruster:
- ion engine: type of electrical spacecraft engine
ionic bond:
- adsorption: adhesion to a surface
- ion: non-neutral atom or molecule, with missing or extra electrons
- oxidation state: number characterizing atoms of a compound as ions
ionic ocean:
- zonal flow: east-west air circulation
ionization:
- acidity (pH): measure of the activity of hydrogen ions in a solution
- binding energy: energy needed to separate two objects
- dark age: interval when the universe's hydrogen atoms were neutral
- degree of ionization: fraction of material consisting of ions
- epoch of reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- HII region (HII): cloud of partially-ionized atomic hydrogen
- instability strip: region of H-R diagram where stars are unstable
- ion: non-neutral atom or molecule, with missing or extra electrons
- ionization correction factor (ICF): relations between ion abundances and element abundances
- ionization fraction: a substance's ratio of unattached electrons to nuclei
- ionization potential: energy needed to ionize an atom
- ionized hydrogen (HII,H II): state of hydrogen when sufficiently hot
- ionizing radiation: radiation with photon energy sufficient to ionize
- kappa mechanism (κ-mechanism): stellar instability caused by opacity increasing with temperature
- LINER: galaxy nucleus emitting spectral lines for ionized and neutral atoms
- neutral atomic hydrogen (HI,H I): state of hydrogen when sufficiently cool
- partial ionization zone: portion of some stars where gas is partially ionized
- photodissociation region (PDR): cloud of partially-ionized atomic hydrogen
- recombination: time when the universe's ionized hydrogen atoms neutralized
- Saha equation: equation relating ionization to temperature
- state of ionization: difference in an ion's electron count versus proton count
- Strömgren sphere: sphere of ionized hydrogen around an OB star
- Z+: symbol for ion or ion charge
ionization correction factor (ICF): relations between ion abundances and element abundances
ionization energy:
- ionization potential: energy needed to ionize an atom
ionization fraction: a substance's ratio of unattached electrons to nuclei
ionization front:
- molecular hydrogen dissociation front (H₂ dissociation front): point in a gas cloud where it is hot enough to dissociate hydrogen
ionization potential: energy needed to ionize an atom
ionization state:
- Saha equation: equation relating ionization to temperature
ionization temperature:
- temperature: measure of hotness/coldness of matter
ionization valve:
- kappa mechanism (κ-mechanism): stellar instability caused by opacity increasing with temperature
ionize:
- state of ionization: difference in an ion's electron count versus proton count
ionized carbon fine structure line ([CII]): carbon line that traces distant star formation
ionized carbon forbidden line:
- ionized carbon fine structure line ([CII]): carbon line that traces distant star formation
ionized hydrogen (HII,H II): state of hydrogen when sufficiently hot
ionized interstellar medium:
- interstellar medium (ISM): matter within a galaxy between star systems
ionizing radiation: radiation with photon energy sufficient to ionize
- extreme ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10-124 nm
ionosphere: layers of Earth atmosphere with significant ions
- space weather: varying conditions in space affecting Earth and humans
ions:
- spark chamber: type of ion detector
IOTA: past optical interferometer in Arizona
IPAC: Caltech group to collect and analyze infrared observations
IPC:
- HEAO-2: 1978 X-ray observatory space mission
IPHAS: H-alpha survey
IPM:
- interplanetary medium (IPM): matter in the solar system around and between planets
IPMO:
- planetary mass object (PMO): has the mass of a planet
IPTA:
- International Pulsar Timing Array (IPTA): organization of pulsar timing arrays
IPTA+:
- International Pulsar Timing Array (IPTA): organization of pulsar timing arrays
iPTF:
- Palomar Transient Factory (PTF): survey designed to find transients
IR:
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
IR excess:
- infrared excess (IRX): more infrared than that of a star's typical spectrum
IR SFR:
- star formation rate (SFR): rate at which material such as gas is turned into stars
IR star formation rate:
- star formation rate (SFR): rate at which material such as gas is turned into stars
IRAC:
- Spitzer Extragalactic Representative Volume Survey (SERVS): infrared survey of some well-studied fields
- Spitzer Space Telescope (SST): past a satellite with infrared telescope
IRAIT:
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
IRAM:
- COLD GASS: survey of CO in nearby large galaxies
- GISMO: 2 mm bolometer camera on IRAM 30 m telescope
- Institut de radioastronomie millimétrique (IRAM): organized radio astronomy collaboration between France, Germany, and Spain
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
- Northern Extended Millimeter Array (NOEMA): large radio telescope array under construction in Europe
- PHIBSS: survey of CO in distant galaxies
- Plateau de Bure Interferometer (PdBI): 6-dish interferometer in French Alps
IRAM 30m Millimeter Radio Telescope:
- IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
IRAM 30m Telescope: millimeter-range radio telescope in Sierra Nevada, Spain
IRAS: 1983 satellite that surveyed the sky in infrared
IRAS 16293-2422:
- ALMA-PILS Survey: millimeter survey of a protostar
IRAS F:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRAS Faint Source Catalog:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRAS Minor Planet Survey:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRAS Point Source Catalog:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRAS-FSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRAS-PSC:
- IRAS: 1983 satellite that surveyed the sky in infrared
IRC:
- AKARI: Japanese space infrared telescope
- Two Micron Sky Survey (IRC,TMSS): 1969 infrared catalog produced by Caltech
IRCAM:
- Hawaii K-band Galaxy Survey: near-infrared survey of a selection of fields
IRCS:
- Subaru Telescope: 8.2 meter telescope in Hawaii
IRD:
- Subaru Telescope: 8.2 meter telescope in Hawaii
IRDC:
- infrared dark cloud (IRDC): molecular cloud not emitting nor transmitting infrared
IREM:
- INTEGRAL: European gamma ray observatory-satellite
iridium:
- siderophile: material that dissolves in molten iron
IRIS:
- AKARI: Japanese space infrared telescope
- Thirty Meter Telescope (TMT): extremely large telescope planned for Hawaii
- Voyager: space probes to observe planets and the edge of the solar system
IRIS2:
- Anglo-Australian Telescope (AAT): 3.9 m reflector telescope in Australia
IRMS:
- Thirty Meter Telescope (TMT): extremely large telescope planned for Hawaii
iron (Fe): metal, Fe, atomic number 26
- iron peak: relatively high abundance of iron and nearby elements
- K-line: iron X-ray line
- Lambda Boötis star (λ Boo): peculiar star with metallicity only with lighter elements
- maximum iron fraction: derived from planet-formation models
- silicon burning: alpha process fusion starting at silicon
- trans-iron element: elements with atomic number greater than that of iron
iron Kα:
- K-line: iron X-ray line
iron K-line:
- K-line: iron X-ray line
iron peak: relatively high abundance of iron and nearby elements
iron star:
- exotic star: term for theoretical stars not made of atoms/ions
iron-56:
- nickel (Ni): metal, Ni, atomic number 28
IRPOL:
- United Kingdom Infrared Telescope (UKIRT): Mauna Kea 3.8 meter infrared telescope
Irr-I:
- irregular galaxy: galaxy that's not a disk or ellipsoid
Irr-II:
- irregular galaxy: galaxy that's not a disk or ellipsoid
irradiance: EMR power reaching a surface
irregular:
- Canis Major Dwarf Galaxy: small irregular galaxy in the Local Group
- Sagittarius Dwarf Irregular Galaxy (SagDIG): most distant galaxy in the Local Group
- Wolf-Lundmark-Melotte (WLM,DDO 221): irregular galaxy at edge of Local Group
irregular galaxy: galaxy that's not a disk or ellipsoid
- galaxy: gravitationally-bound group of stars
- galaxy classification: morphological classification of galaxies
irregular moon: moon with an atypical orbit, such as retrograde
irregular satellite:
- irregular moon: moon with an atypical orbit, such as retrograde
IRS:
- Spitzer Space Telescope (SST): past a satellite with infrared telescope
IRSA: archive center for infrared data from NASA missions
IRSF:
- Infrared Survey Facility (IRSF): 140 cm reflector telescope that images in infrared
- South African Astronomical Observatory (SAAO): South African observatory with SALT telescope
IRTF: Mauna Kea 3-meter infrared telescope
- Mauna Kea: Hawaiian mountain, the site of observatories
- Mauna Kea Observatories (MKO): observatories on Mauna Kea in Hawaii
IRTS:
- Japan Aerospace Exploration Agency (JAXA): Japan agency includes astronomical research
IRX:
- infrared excess (IRX): more infrared than that of a star's typical spectrum
ISAAC:
- European Southern Observatory Very Large Telescope (ESO VLT,VLT): four 8.2-meter optical telescopes in Chile that can act together
Isaac Newton Group of Telescopes (ING): three telescopes in Canary Islands
- Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
Isaac Newton Telescope (INT): 2.5 m telescope in Canary Islands
- IPHAS: H-alpha survey
- Isaac Newton Group of Telescopes (ING): three telescopes in Canary Islands
- POINT-AGAPE: survey of M31 for microlensing
- Roque de los Muchachos Observatory (ORM,LPO,NHO): observatory at La Palma in the Canary Islands
ISAMS:
- Upper Atmosphere Research Satellite (UARS): 1990s spacecraft to observe Earth ozone layer
ISCO:
- innermost stable circular orbit (ISCO): border of region surrounding a BH in which orbits are unstable
ISCO-radius:
- innermost stable circular orbit (ISCO): border of region surrounding a BH in which orbits are unstable
ISEE:
- International Cometary Explorer (ICE): 1980s space mission flying by comets
ISEE-3:
- International Cometary Explorer (ICE): 1980s space mission flying by comets
iSEEP Wide-Field MAXI:
- MAXI: Japanese X-ray camera on the International Space Station
ISEM:
- Rosalind Franklin: Mars rover in development for 2020 launch
ISG:
- rare designator prefixes: designator prefixes generally used for only a few objects
ISGRI:
- INTEGRAL: European gamma ray observatory-satellite
iShell:
- IRTF: Mauna Kea 3-meter infrared telescope
ISIS:
- William Herschel Telescope (WHT): 4.2 meter telescope in the Canary Islands
ISM:
- Cloudy: code to model the effect of gas and plasma on spectra
- cold gas: gas cool enough to form galaxies and stars
- galactic disk: the "disk" portion of a disk galaxy
- galactic electron density: density of electrons in the ISM
- interstellar astrophysics: astronomy of the ISM including dust and clouds
- interstellar holography: holographic analysis of incoming EMR to study the intervening ISM
- interstellar medium (ISM): matter within a galaxy between star systems
- Local Interstellar Cloud (LIC): local ISM region with slightly higher density of hydrogen
- refractive interstellar scintillation (RISS): refraction of star light by the ISM
- shell: hollow shaped region of some kind of ISM
- supershell: very large ISM shell-shaped region
ISM cirrus:
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
ISMF:
- interstellar magnetic field (ISMF): galactic magnetic field between that of stars
ISO:
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
ISO spectrum:
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
ISOCAM:
- CEA Service d'Astrophysique (CEA SAp): French national astrophysics research institute
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
isochrone:
- H-R diagram (HRD): diagram relating effective temperature to luminosity
ISOHDFS:
- Hubble Deep Field South (HDF-S): small region of the southern sky explored with HST
isolated neutron star:
- neutron star (NS): stellar remnant consisting entirely of solar masses of neutrons
isolated planetary mass object:
- planetary mass object (PMO): has the mass of a planet
isolation mass: mass of an oligarch after accreting all nearby planetesimals
isolation mass core:
- isolation mass: mass of an oligarch after accreting all nearby planetesimals
isolation mass planet:
- isolation mass: mass of an oligarch after accreting all nearby planetesimals
ISOPHOT:
- Infrared Space Observatory (ISO): 1990s 60-cm infrared space telescope
isophote: line on a diagram indicating a level of brightness
- Holmberg radius (R_H,R_HO): a measure of size of galaxy based on surface brightness
isostasy: crust-mantle equilibrium
isothermal core: core region of a body of all the same temperature
isotope: subclass of an element with a specific number of nucleons
- ¹H: hydrogen isotope with no neutrons
- deuterium (D,²H): hydrogen isotope with one neutron
isotope fractionation:
- fractionation: separation of compounds from a mixture
- fractionation factor: isotope quantity
isotope notation:
- isotope: subclass of an element with a specific number of nucleons
isotope signature:
- Moon formation: process by which the Moon and other moons formed
isotopes:
- element: class of atom based on its number of protons
isotopic fractionation:
- fractionation factor: isotope quantity
isotropic radiant energy:
- isotropy: uniformity in all directions
isotropic radiation:
- isotropy: uniformity in all directions
isotropy: uniformity in all directions
ISPM:
- Ulysses: space mission to observe the Sun from off the ecliptic
ISS:
- Cassini: explorer spacecraft sent to Saturn
- NICER: space X-ray mission specifically to view neutron stars
- scintillometry: measuring of twinkling
- Voyager: space probes to observe planets and the edge of the solar system
ISW:
- Sachs-Wolfe effect (SWE,SWeffect): gravitational redshift of the CMB
ITA:
- Institute of Theoretical Astrophysics (ITA): Heidelberg research institute
Italian:
- AGILE: Italian space gamma-ray observatory
- PAMELA: cosmic ray detector attached to satellite
- Telescopio Nazionale Galileo (TNG): 3.58 m telescope in Canary Islands
Italian National Institute of Astrophysics:
- Telescopio Nazionale Galileo (TNG): 3.58 m telescope in Canary Islands
Italian Robotic Antarctic Infrared Telescope:
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
Italian Space Agency:
- Agenzia Spaziale Italiana (ASI): includes space-based astronomy research
- AGILE: Italian space gamma-ray observatory
Italy:
- Agenzia Spaziale Italiana (ASI): includes space-based astronomy research
- Bologna Survey of Radio Sources: 1970s-1980s radio survey
- Campo Imperatore Near-Earth Object Survey (CINEOS): survey of near-Earth objects
- European Gravitational Observatory (EGO): gravitational wave observatory in Italy
- Sardinia Radio Telescope (SRT): Italian large single-dish radio telescope
- Virgo: ground-based gravitational-wave detector in Italy
ITCZ:
- intertropical convergence zone (ITCZ): circulation pattern near equator where north and south Hadley cells meet
ITEP:
- ITEP-SAI Supernova Light Curve Catalogue: online catalog
ITEP-SAI Supernova Light Curve Catalogue: online catalog
iterative method:
- Krylov subspace method: efficient method of numerically solving sets of linear equations
ITM:
- Infrared Telescope Maffei (ITM,IRAIT): 80 cm infrared telescope in Antarctica
IUE:
- International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
IUE Data Analysis Center:
- International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
IUEDAC:
- International Ultraviolet Explorer (IUE): 1980s ultraviolet space telescope
IUV:
- MAVEN: Mars orbiter to study its atmosphere
IVC:
- high-velocity cloud (HVC): fast-moving clouds in galactic halos
iWF-MAXI:
- MAXI: Japanese X-ray camera on the International Space Station
Ixion:
- trans-Neptunian object (TNO): minor planet beyond Neptune

Index